Step 1

To make the dip, heat the flour, mustard powder and milk in a small saucepan and gently cook, whisking constantly, until smooth. Carry on bubbling and stirring until thickened. Turn off the heat, stir in the cheese until melted, then season to taste. Scrape into a microwave-proof bowl and put some cling film directly on the surface.

Step 2

Heat oven to 220C/200C fan/gas Spread the fries on 1-2 big baking trays and cook for 10 mins, then scatter over the Parmesan and garlic salt – use tongs to toss and coat all the chips in the cheese, then carry on baking for 10 mins more until golden and crisp – if the chips aren’t crispy enough, increase oven to 240C/220C fan/gas 9 for a few mins.

Step 3

Gently reheat the dip in the microwave until warm, stir in the chives and serve with the hot chips.